There are many specific treatment procedures which involve directing a highly controlled beam of electromagnetic radiation to an eye. For example, one specific surgical procedure that has been described involves using a radiation beam to ablate and thus cut portions of the corneal tissue. A specific application of this surgical procedure is in the performance of a radial keratotomy procedure, in which radial cuts are made in the cornea using a laser as opposed to a surgical knife. In another specific treatment procedure, an outside surface of the cornea is removed by an excimer laser in order to reshape it. Despite the existence of the aforementioned specific procedures, alternative "keratoplasty" procedures are currently receiving a great deal of attention because of their ability to correct for near-sightedness, far-sightedness and/or astigmatism.
In a particular keratoplasty procedure, which avoids cutting or ablating any portion of the cornea, at least one focused beam of electromagnetic radiation within the infrared portion of the spectrum is directed into the eye to shrink collagen tissue within the cornea in order to cause corrective changes in corneal curvature. This technique, often termed "photothermal keratoplasty", "laser thermal keratoplasty", or "laser thermokeratoplasty" is the subject of U.S. Pat. Nos. 4,976,709 and 5,618,284 to Bruce J. Sand (hereinafter, "the Sand Patents"), where the technique is described to be carried out with a holmium:YAG laser. The Sand patents are expressly incorporated herein in their entireties by this reference. This collagen shrinkage technique promises to provide permanent changes to the optical characteristics of the human cornea with a higher degree of safety and patient comfort than that provided by techniques that involve physically cutting and removing portions of the cornea.
One way to deliver a desired electromagnetic radiation pattern to the cornea is by projection from a short distance removed from the cornea. One instrument for doing so is described in the Published International Patent Cooperation Treaty Application WO 94/03134 (hereinafter, "the PCT Publication"), which publication is expressly incorporated herein in its entirety by this reference. This instrument allows an ophthalmologist, or other attending physician or practitioner, to select and to deliver a specific pattern and amount of electromagnetic radiation to each patient in accordance with the condition to be corrected. It is desirable for such an instrument to perform efficient corrective photothermal keratoplasty procedures on a large number of patients with a high degree of accuracy, effectiveness, safety and convenience.
The aforementioned Third Co-Pending Application discloses apparatus and methods for applying a flow of a conditioning or drying medium to an external surface of an eye of a patient, to dry the eye in preparation for ophthalmological observation and/or treatment. Such apparatus and methods are particularly useful in to prepare a patient's eye for vision-corrective ophthalmological treatments, such as photothermal keratoplasty, wherein a defined pattern of electromagnetic radiation is delivered to an external surface of the cornea in a controlled manner for the purpose of reshaping the cornea. The aforementioned First and Second Co-Pending Applications describe a system and methods for using the system to expose an eye of a patient to a controlled pattern of radiation and for holding the head of the patient in preparation for and during such exposure.
It is desired to make the exposure system as automated as reasonably possible for determining a pattern of radiation exposure that is appropriate to correct the vision of a particular eye of a patient, for preparing the eye for such an exposure and for then exposing the patient's eye to that pattern of radiation, all with convenience and efficiency for an attending physician or other provider of the treatment.